Are ring galaxies the ancestors of giant low surface brightness galaxies?

Giant low surface brightness galaxies (GLSBs), such as Malin 1, have unusually large and flat discs. Their formation is a puzzle for cosmological simulations in the cold dark matter scenario. We suggest that GLSBs might be the final product of the dynamical evolution of collisional ring galaxies. In fact, our simulations show that, approximately 0.5-1.5 Gyr after the collision which lead to the formation of a ring galaxy, the ring keeps expanding and fades, while the disc becomes very large (similar to 100 kpc) and flat. At this stage, our simulated galaxies match many properties of GLSBs (surface brightness profile, morphology, H 1 spectrum and rotation curve). (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim